《Anodizing Aluminum》.pdf

Anodizing Aluminum By J.C. HECKER, JR. Aluminum Consultants Madison, Wisconsin Anodizing, unlike electroplating and Anodized aluminum is easy to clean organic coatings, is commercially unique and resists heat to the temperature at to aluminum. Developed in the early which the aluminum itself melts. 1930’s, it has greatly extended the appli- cations of aluminum in products and uses Coating Formation where the metal might otherwise not be Anodizing is an electrochemical con- utilized. The finish is readily available version process, not an applied coating. from finishing job shops throughout the The surface of the aluminum metal is con- world and is relatively inexpensive. verted to aluminum oxide as a result of Anodizing converts the surface of alu- reactions occurring at the anode in an minum to an oxide. While aluminum nat- acidic solution. The thickness and proper- urally forms aluminum oxide on its sur- ties of the anodic coating will vary with face, this is a very thin film. Anodizing alloy, anodizing process employed and provides a much thicker oxide coating- cycle time (ampere-hours). several mils thick if required. Oxide formation proceeds inward, to- ward the source of fresh metal. The first C o a t i n g P r o p e r t i e s formed oxide remains in contact with the The hardness of this aluminum oxide anodizing solution throughout the proc- co